Four billion years of evolution in six minutes

If we evolved from monkeys,
why are there still monkeys?

(Laughter)

Well, because we're not monkeys,

we're fish.

(Laughter)

Now, knowing you're a fish
and not a monkey

is actually really important
to understanding where we came from.

I teach one of the largest
evolutionary biology classes in the US,

and when my students finally understand
why I call them fish all the time,

then I know I'm getting my job done.

But I always have to start my classes
by dispelling some hardwired myths,

because without really knowing it,
many of us were taught evolution wrong.

For instance, we're taught
to say "the theory of evolution."

There are actually many theories,
and just like the process itself,

the ones that best fit the data
are the ones that survive to this day.

The one we know best
is Darwinian natural selection.

That's the process by which organisms
that best fit an environment

survive and get to reproduce,

while those that are less fit
slowly die off.

And that's it.

Evolution is as simple as that,
and it's a fact.

Evolution is a fact
as much as the theory of gravity.

You can prove it just as easily.

You just need to look at your bellybutton

that you share
with other placental mammals,

or your backbone that you share
with other vertebrates,

or your DNA that you share
with all other life on Earth.

Those traits didn't pop up in humans.

They were passed down
from different ancestors

to all their descendants, not just us.

But that's not really
how we learn biology early on, is it.

We learn plants and bacteria
are primitive things

and fish give rise to amphibians
followed by reptiles and mammals,

and then you get you,

this perfectly evolved creature
at the end of the line.

But life doesn't evolve in a line,

and it doesn't end with us.

But we're always shown evolution
portrayed something like this,

a monkey and a chimpanzee,

some extinct humans,

all on a forward and steady march
to becoming us.

But they don't become us
any more than we would become them.

We're also not the goal of evolution.

But why does it matter?

Why do we need to understand
evolution the right way?

Well, misunderstanding evolution
has led to many problems,

but you can't ask that age-old question,

"Where are we from?",

without understanding
evolution the right way.

Misunderstanding it has led
to many convoluted and corrupted views

of how we should treat
other life on Earth,

and how we should treat each other

in terms of race and gender.

So let's go back four billion years.

This is the single-celled organism
we all came from.

At first, it gave rise
to other single-celled life,

but these are still evolving to this day,

and some would say
the Archaea and Bacteria

that make up most of this group

is the most successful on the planet.

They are certainly going
to be here well after us.

About three billion years ago,
multicellularity evolved.

This includes your fungi
and your plants and your animals.

The first animals to develop
a backbone were fishes.

So technically,
all vertebrates are fishes,

so technically, you and I are fish.

So don't say I didn't warn you.

One fish lineage came onto land

and gave rise to, among other things,
the mammals and reptiles.

Some reptiles become birds,
some mammals become primates,

some primates become monkeys with tails,

and others become the great apes,
including a variety of human species.

So you see, we didn't evolve from monkeys,

but we do share
a common ancestor with them.

All the while, life
around us kept evolving:

more bacteria, more fungi,
lots of fish, fish, fish.

If you couldn't tell --
yes, they're my favorite group.

(Laughter)

As life evolves, it also goes extinct.

Most species just last
for a few million years.

So you see, most life on Earth
that we see around us today

are about the same age as our species.

So it's hubris,
it's self-centered to think,

"Oh, plants and bacteria are primitive

and we've been here
for an evolutionary minute,

so we're somehow special."

Think of life as being this book,
an unfinished book for sure.

We're just seeing the last
few pages of each chapter.

If you look out
on the eight million species

that we share this planet with,

think of them all being
four billion years of evolution.

They're all the product of that.

Think of us all as young leaves
on this ancient and gigantic tree of life,

all of us connected by invisible branches
not just to each other,

but to our extinct relatives
and our evolutionary ancestors.

As a biologist, I'm still
trying to learn, with others,

how everyone's related to each other,
who is related to whom.

Perhaps it's better still

to think of us
as a little fish out of water.

Yes, one that learned to walk and talk,

but one that still has
a lot of learning to do

about who we are and where we came from.

Thank you.

(Applause)